Radio wave focusing device



Sept. 4, 1951 H. lAMs RADIO WAVE FOCUSING DEVCE Filed May 14,A 1947 3 Sheets-Sheet 1 INVENTOR.

Haley lams Bf @La ATTORNEY Sept. 4, 14951 H. [AMS 2,566,703

RADIO WAVE FOCUSING DEVICE Filed May 14. 1947 3 Sheets-Sheet 2 Harle Iams BY' l l ATTORNEY INVENTOR.

Sept. 4, 1951 INVENTOR.

Harley Iams ATTORN EY Patented Sept. 4, 1951 RADIO WAVE FOCUSING DEVICE Harley Iams, Princeton, N. J., assigner to Radio Corporation of America, a corporation of Dela- Ware Application May 14, 1947, Serial No. 747,889

13 Claims. (Cl. Z50-33.65)

This invention relates to the art of focussing radio and similar waves, and more particularly to devices of the type in which the different parts of a wave front are made to follow paths of such length as to bring them into phase at a focal point. It is known that lenses, designed like those used for optical purposes, may be used for focussing radio waves. Such lenses may be made of dielectric material, such as paraffin wax. The present invention differs in that it contemplates the use of a plurality of conduits, for example waveguides or transmission lines, arranged to change the shape of a wave front by accepting the Wave energy at points lying in one line or surface and radiating the energy from corresponding points lying in another line or surface. These structures exhibit the properties of lenses, such as the ability to focus and form images, but operate on principles somewhat different from those used in optical devices.

The invention will be described with reference to the accompanying drawings, wherein:

Figure 1 is a plan view of a portion of a focussing device which embodies the present invention,

Figure 2 is a section of the device in Figure 1 taken in the plane designated by the line 2-2 of Figure 1,

Figure 3 is a schematic representation of a modification of the device of Figure 1,

Figure 4 shows schematically a further modilication of the device of Figure 1,

Figure 5 shows a device similar to that of Figure 3 but extended to provide two-dimensional images,

Figure 6 is a perspective View of a focussing device constructed in accordance with the instant invention, using hollow waveguides, and

Figure 7 is a perspective view of a device like that of Figure 6 but of slightly different design.

The device illustrated in Figures 1 and 2 is for focussing waves guided between parallel conductive sheets. Both the upper and lower sheets I and 3 respectively are shown in Figure 2. In Figure 1 the upper sheet is omitted to reveal the structure. A plurality of rod-like antenna elements 5 are disposed in a circular are extending across the sheet 3. The rods 5 extend approximately one-quarter wavelength from the surface of the sheet 3, and are spaced along the arc at equal intervals of about one-half wavelength.

A second group of antenna elements 'l is arranged similarly along another circular arc, at half wavelength intervals. The elements 1 are equal in number to the elements 5, and each element 'I is connected to a corresponding one of the elements 5 by a respective transmission line 9. vThe lines 9 are all of the same length, or all have the same effective or electrical length on a wavelength scale for the energy propagated therethrough. Y

Reflectors II and I3 are provided between the rows of antennas 5 and l. The reflector II is curved substantially like the arc along which the antennas 5 are disposed, and is located about one-quarter wavelength away from it. The reector I3 corresponds in shape to the arc delined by the antennas l, and lies about onequarter` wavelength outside said arc. n

The radius of the arc formed by the antennas 5 is approximately twice that of the antennas 'I. A further antenna I5 is .provided at a point which is approximately on the circle drawn through antennas l. The antenna I5 is connected by a transmission line I'I to a utilization device such as a transmitter or a receiver, not shown.

The operation of the described device is substantially as follows: Suppose'a plane wave, such as that from a distant source, to be arriving from the left of Figure 1. kA phase front, or line of points of equal phase, in such a wave is a straight line perpendicular to the direction of travel. Any particular phase iront arrives first at the central antennas 5, and progressively later at the others, reaching finally the outermost of -the antennas 5. The phases at the antennas 'I lag those at the corresponding antennas 5 by equal amounts, since the lines 9 are of equal lengths. Thus the excitations of the antennas 'I'are progressively more lagging, going from the center to the outsideiof the group.

The resultant phase front formed by radiation from the antennas 1 is curved with a radius 2R, where R is the radius of curvature of the locus 0f the antennas 'I and 2R is the radius of the locus of the antennas 5.] The center of curvature of this phase front is at the antenna I5, so that substantially all of the energy picked up by the antennas 5 arrives inv phase at the antenna I5.

The device also operates for transmission; if the antenna I5 is supplied with energy from a source connected to the line I'I, the portionV of the resulting circular wave front which strikes the antennas 'I ls converted to a plane wave travelling to the left from the antennas 5.

The uses are not limited to conversion between a plane Wave and a curved wave of radius 2R. As in optical lens systems, a wave front of one curvature may be converted to one of va different 3 curvature. The distance 2R may be considered as the focal length F of the system. A wave front of any radius Ra arriving at one row of antennas is radiated from the other row as a wave front of radius Rb, where Rs and Rb are related as follows:

Preferably the system should be arranged so A that the wave front of greater radius should be associated with the antennas 5, in order to minimize aberration.

The invention is not restricted to the-particular dimensional relationships shown Iin Figure 1. For example, as shown schematically in Figure 3, one row of antennas 2| may be disposed at equal intervals along a straight line, and connected by equal-length lines 23 to corresponding antennas '25 which lie on an arc of radius R. In this example, the'antenna's are placed at equal intervals from the anis A21 instead of equal intervals along the arc.

The device 4of Figure 3 exhibits substantially the same 'characteristics as that of Figure 1, with the exception that it focal lengthsis R rather than 2R. The focal line, which is the locus of focal points for plane :waves arriving at the an'- tennas 2| at various 4angles to the vaxis 2l, is curved, as indicated 'by the dash -line' '29 in YFigure 3. This e'iect is Kanalogous to that of curva'- ture of the field in 'optical systems.

In the system of 'Figure 4, the antennaelements 3| are Vlocated 'at -equal 'intervals along a straight line, like the "elements 21 in Figure 3. Elements 35 are arranged 'along an arc 'of ra#- dius R, like the elements 25 of Figure 3, and are connected to the 4corresponding elements 3| by lines 33. The distanoeo'f vthe elements 35 from the `axis is however;` l/h times that of the corresponding elements 3|.

The structurefof Figure 4 'operates 'as a lens of focal length R, like 'the 'devicejof Figure 3. In addition, it has the property of multiplying any deviation'of /thedireotion of 'travel-of a wave by the factor h or '1j/n, 'dependii'giupon whether the wave goesfonfleft to Lright'or from right to left in Figure '4. This "function is 'particularly useful in devices 'for scanning, where it is Vdesirable to have a'sli't fooal `length to minimize the dimensions of the 'apparatuaand yet va large aperture to Jl'riniin'iz'e 'the l'oearn Width. Also, for direction nding'it is convenient to 'have the `an` gular position '"o`f 'an Y antenna device, such as a horn Vfl change by "a 'factor 'of 'approximately n0 where the position of a'ta'get'inove's through an angle 0. I

The devices thus 'far deseribed'are all intended for operation with "energy "confined to substantially a single plane, su'ch'as the space between the upper and Ylower sheets v| and '3 in Figure 2, and the wavefronts may be regarded as lines. When propagation occurs in Amore or less uncon-' .fined space, Vthe wave fronts are generally surfaces, rather than lines. Such waves can be handled by structuresanalogous to those of Figures 1, 3 and 4, but extended in another dimension.

Referring to Figure 5, a plurality of antennas 43 are distributed uniformly near the surface of a fiat reflector 45. Each antenna 43 is connected through a line 49 to a corresponding one of a group of antennas 41, disposed adjacent a spherical reflector The lines 49 are all of the same'ele'ctrical length.

The device of Figure 5 is analogous to that of Figure 3, and each elementary row of antennas functions like the structure of Figure 3. The complete structure will accept a wave front in the form of a surface of one curvature and deliver a wave front whose surface is of a different curvature. Ilghe focal length of the device, considered as a lens, is equal to thenradius of curvat'r'e Aof the reflector 5|. It will b'e vapparent Without further discussion that similar analogies eiist for the devices of Figures 1 and 3.

Referring to Figure 6, a number of waveguides are assembled so that their openings at one end for'in a 'straight line '63, while the other ends form a 'curved line 65. The waveguides 6| are of equal lengths, so that a rectilinear wave front striking the yline 63 produces a curved wave front at the line 55, bringing energy to a focus at the center of "c''ryature of the line 65.

Figure 7 shows a struoture differing from that of Figure 6 only in that the waveguides 61 are curved back vso that energy passing through the devices Jcontinues in the same general direction instead of travelling back `toward the source. The electrical Hchar'ac'teri'sti'c s "of the device 'of FigureWa're substantially identical with those of the structure of Figure 3. The mouths or openings of the waveguides "function 'as antennas, and the waveguides 'actas transmission lines. y

Theproportionswhich have been given in this discussion 'are those of radio wave vfocusing `vde'- vices which have low aberration, :even for points at considerable distance 'fiorntheoptic axis. For some Vpurposes it is not necessary to meet this re"- q'uiremerit, andfoth'e'r 'radii for shapes may be used for the surfaces fon which the "wave 'cl'lecting and radiating elements 'are .pla'ced.y The focal length F 'of the 'device may then be found from the following formula:

.'FRI''T,

where R1 and R2 A:are the 'radii 'of the two surfaces.

, lgclaim as my invention: 1.l s'ystern .'forfocussing radiant energy, Comprising a plurality ofwave collector elements disposed at sulfistantially equally spaced points on a surface, a reiiector 'positioned with said "collector elements `between itA and the source of the incident energy to be focused, a plurality of radiator elements 'disposed 'at substantially equally 'spaced points 'on a second surface, a secondreii'ectorpsitioned with saidradiator ele'A ments between 4it and the place toward which the energy is to 'be radiated "by said 'radiator elernents, 'at 'least'oiie ofsaid surfaces' being curved, and 'respectively' separateV and 'independent means connecting each 'of lsa'id collector means which occupies 4'a positionfon said ''rst surface to the one u'ari'd'lcjnly one of'lsaid 'radiatormeans which occupies the vcor'rfe'spo'ridi'ng position `on said s'e'condsur'faoe, said c'olinectingimeansbeingof equal eifec't'ive "electrical lengths whereby said energy is "focused 'by "said Aradiator elements.

2. A system for focussingfadiant energy, A'co'rnprising a pluralityof 'vvave'V collector*elehiients disposed at r'substantially equal intervals Yalong `a line, "a reflector positioned with sa'id 'collector elementsbetween it and Ethe source of the incident energy to be focused,'a pluralityofradiator elements -`disposed at substantially equal intervals'along `a second linea-"second reflect'o'rl'posi tioned with said `radiator elements 'between .it and the place toward *whichthe teifiere'y is to be atea-ros radiated by said radiator elements, at least one of said lines being curved, and respectively separate and independent means connecting each of said collector1 means which occupies a` position along said rst line to the one and only one of said radiator means which occupies the corresponding position along said second line, said connecting means being of equal eifective electrical lengths whereby said energy is focused by said radiator elements.

3. A system for focussing radiant energy, comprising a plurality of wave collector elements disposed at substantially equal intervals alongv a line, a reflector positioned with said collector elements between it and the source of the incident energy to be focused, a plurality of radiator elements disposed at substantially equal intervals along a second line, a second reflector positioned with said radiator elements between it and the place toward which the energy is to be radiated by said radiator elements, said intervals along said second line being different from those along said iirst line, at least one of said lines being curved, and means connecting each of said collector means which occupies a position along said first line to the one and only one of said radiator means which occupies the corresponding position along said second line, said connecting means being of equal effective electrical lengths whereby said energy is focused by said radiator elements.

4. A system for focussing radiant energy comprising a plurality of energy collector means at point defining a first surface, a reflector positioned with said collector means between it and the source of the incident energy to be focused, a plurality of radiator means at points defining a third surface, a second reflector positioned with said radiator means between it and the place toward which the energy is to be radiated by said radiator means, at least one of said first and third surfaces being curved, and a plurality of linear wave transmission devices, each connecting only one of said collector means on said first surface to only one of said radiator means at a corresponding position on said third surface, said wave transmission devices being of substantially equal effective electrical lengths whereby said energy is focused by said radiator means.

5. A system for focussing radiant energy comprising a plurality of energy collector means at points defining a line, a reiiector positioned with said collector means between it and the source of the incident energy to be focused, a plurality of radiator means at points defining a second line, a second reflector positioned with said radiator means between it and the place toward which the energy is to be radiated by said radiator means, at least one of said lines being curved, and a plurality of linear wave transmission devices, each connecting only one of said collector means to only a corresponding one of said radiator means, said wave transmission devices being of substantially equal effective electrical lengths whereby said energy is focused by said radiator means.

6. In a radio device including at least two par allel conductive sheets forming waveguiding means, a reflector extending between said two sheets substantially transversely to the direction in which energy is to flow through said guide, a plurality of wave collector elements adjacent said reflector at spaced points dening a line, a second reflector between said sheets and substantially transverse to said direction of energy ow,

aplurality 'of radiator elements,adjacentsaid second reflectorat spaced points defining a second-line, and means of substantially equal electrical lengths connecting eachof said radiators to a correspondingoneof said collectors; at least one of the linesdened by said collector elementsand said radiator elements being curved, whereby energy owing through said device is focussed at points outside said two lines.

7. In a radio device including at least two-parallel conductive sheets forming a waveguiding means, a plurality of wave collector elements` at spaced points defining a line extending substantially transversely ,tog-the.- direction in which energy is to flow through said guide, a plurality of radiator elements at spaced points defining a second line substantially vtransverse to said direction of energy iiow, and means of substantially equal electrical lengths connecting each of said radiators to a corresponding one of said collectors; at least one of the lines defined by vsaid .collector elements and said radiator elements being curved, whereby energy iiowing through said device is focussed at points outside said two lines.

8. In a radio device including at least two parallel conductive sheets forming waveguiding means, a plurality of wave collector elements at spaced points dening a line extending substantially transversely to the direction in which energy is to flow through said guide, a plurality of radiator elements at spaced points defining a. second line substantially transverse to said direction of energy flow, and means of substantially Y equal electrical lengths connecting each of said radiators to a corresponding one of said collectors; one of the lines defined by said collector elements and said radiator elements being curved, and utilization means substantially at the center of curvature of said line.

9. In a radio device including at least two parallel conductive sheets` forming waveguiding. means, a plurality of wave collector elements at spaced points dening a curve line extending substantially transversely to the direction in which energy is to flow through said guide, a plurality of radiator elements at spaced points defining a second curved line substantially transverse to said direction of energy flow, the radius of curvature of one of said lines being twice that of the other of said lines, and means of substantially equal electrical lengths connecting each of said radiators to a corresponding one of said collectors.

10. In a radio device including at least two parallel conductive sheets forming waveguiding means, a reflector extending between said two sheets substantially transversely to the direction in which energy is to ow through said guide, a plurality of wave collector elements adjacent said reiiectorat spaced points dening a curved line of radius 2R, a second reiiector between said sheets and substantially transverse to said direction of energy iiow, a plurality of radiator elements adjacent said second reector at spaced points deiining a second curved line of radius R, and means of substantially equal electrical lengths connectingV each of said radiators to a corresponding one of said collectors; and a utilization device at a point distant substantially 2R from the center of said second line.

11. In a radio device including at least two parallel conductive sheets forming waveguiding means, a reflector extending between said two sheets substantially transversely to the direction in which energy is to flow through said guide, a.

1 fsi'uraiity of' weve collectorA elements adjacent said. reflector at spaced points de'ning a curved line of radius R1, a second reector between said sheets and substantiallyV transverse t said direction of energy 110W, a plurality of radiator ele ments adjacent said second reiictor at spaced points defining a second curved line f radius R, and means of substantially equalA electrical lengths connecting eachf said radiztz-s t a corresponding one of said' collectors; and utilization. means at a distance of substantiel-1v1 from the' Center Of Grie- O`15 Said line's, Whef 1 1- 1 Fle; 12. The' system claimed in elaimy 5,- sai'd trans: mission devices con'ipris'ingfr waveguides.

13. The system claimed in claim 5'-, said crans-l mission devicescomprising waveguides, said lines each` being a curve of substantially uniform radius,x n

HARLEY IAMS.

R'FRNCS oiTEi The following references are of re'oo'rd in the lev of this patent:

UNITED STATES PATENTS Number Name Date Stone June 9; 1,821,386 Lindeblad Sept. 1, 1931 1,908,595 Franklin et a1. May 9, 1933 1,918,291 Schroter July 18', 19'33 '2,155,821 Goldsmith A131225', 1939 2,272,312 Tuniek- Feb. 10,- 1942 2,276,497 Koger Mai". 17, 1942 Peterso Jan. Lindenblld 2,311,467 Peterson Feb. 16,1943: '2,398,095 Katzin Apr. 9,- 1946 2,405,242 Southworth Aug. 6,- 1946 2,445,895 Tyrrell July 27, 1948' 2,471,515 Brown-etV al. May 31, 1949 

